A possible explanation to the accelerated expansion of the Universe is that the energy density contains a contribution from a dynamical scalar field, i.e. so-called quintessence. The problem with this explanation is that since the scalar field will couple to matter, it will give rise to a long-ranged fifth force unless the coupling is tuned to unnaturally small values. Hence we often end up with models that are in conflict with known tests of gravity. In this thesis I have studied so-called chameleon fields, which is a scalar field theory for cosmic acceleration consistent with known constraints on the fifth force.

Chameleon field theory is a kind of scalar-tensor theory of gravity. Einstein's general theory of relativity is a pure tensor theory, while the first known scalar-tensor theory was the Brans-Dicke theory. General relativity predicts the existence of gravitational waves. Such waves have never been observed directly, but from observations of the Hulse-Taylor pulsar, one has obtained indirect evidence for their existence.

Gravitational waves in scalar-tensor theories do not behave exactly as they to in general relativity. The goal with my master thesis was to calculate the radiated effect in form of gravitational waves from a quadrupole source in chameleon field theory, and compare the results to those found in general relativity.